Slower and not quite so good as the primes, but useful
john
Yes, the primes are sharper and faster, 1/2 stop on the wide end and two on the long. But you do not have to change lenses in fast moving situations. Changing lenses quickly on the S is a challenge, with the weight and bulk of body and lens, it is not as graceful as changing on the M.
As I said, the 45 is without peer, I can see the difference in image quality with this lens compared to the 30 prime. Both my 30 and 70 did not have CS which I like to have for flash work so they were sacrificed in favor of the 30-90. If I find a 70 CS in the future I may pick it up, as far as the 30, I may instead get the 24. Looking at some same subject matter shot on the 30 prime and 30-90 zoom, I do not see that much of a difference. Corners on the 30-90 are softer than the 30 prime, overall sharpness is like splitting hairs.
In the end it is a matter of matching the lens to the subject matter. Casual shooting lends itself to the zoom purely for convenience. If I had a specific subject that I wanted to capture, primes are my first choice. Most of my subjects in that case would be shot with the 45 or 120. I really resisted getting the zoom for two years and in the end, the zoom won out for convenience.